Room in Bird?

[Creemy]

Getting ready to order servos for a Big Bird. I'm thinking 81MGs for main controls and plain 81s for spoilers. 55s seem a bit weak but I know from various threads that they will work but also that there should be enough room in the wing for 81s. Any comments? Additionally what's the largest square battery pack than can be sqeezed into the Bird's nose? It'd be nice to be able to stuff a 1400mah square pack in there if possible but if only a 600 will fit so be it. Thanks for any replies---Mark

[aeajr]

I don't have your plane so I can't give you specifics, but I can make this suggestion. If you built the plane and are now ordering the electronics, do a test balance.

Sometimes the extra weight of a larger servo actually helps you balance the plane and potentially saves you money over smaller stuff.

I have 81 and 81 MGs in several planes. They work finea and have plenty of torque. However I am moving more toward the 85-MG BB servos now for better centering and smoother operation. You might give that some consideration, especially for the elevator. A little drift on the elevator can make a big difference, as was recently pointed out to me.

85s will be about $5-7 more per servo, so the jump is not a lot.

Good luck with your big bird.

[Ollie]

In a ground loop landing, the rudder servo has a large load from grass or rough ground. I would pick a standard servo for strong gears and low price.

[Creemy]

85MG BBs for the mains sound good. They have more precision and torque equal to nominal "standard" servos but in a smaller tougher package that shouldn't strain the confines of a Bird fuselage. I presume that plain old 81s have plenty of oomph for spoilers but that still leaves the question of whether there is room up front for more than a square 600mah batt. pack. The last sailplane I built, a much loved Sagitta 900, was a challenge to cram standard sized gear into. That build was so long ago, 1980, and small servos of the day weren't remotely as crisp and powerful as today's offerings.

Servo City indicates that a 1450 NiMh square pack is nearly identical in size and weight compared to a 600 Nicad pack so maybe that's the way to go. I certainly needed extra capacity, and nose weight, on the Sagitta and by all indications the Big Bird flys just as well if not considerably better. I'd like to get my hands on one of the Aerosphere Sagitta kits when they come out but that's looking to take quite bit longer than I want to wait. I seriously loved that airplane. It wasn't a light build but I specked it out innumerable times and it penetrated nicely in gusty East Texas winds. It was purty too.

[varoman1]

I have been flying my Big Bird for nearly two years and it is a terrific plane. It came in at 41 oz. I have about 1oz wt, a 700mah nicad pack, two Airtronics standard size servos end- to- end and a Hitec 555 receiver. A hatch over the wing carries a Hitec 225 mg servo pulling kevlar thread that opens the spoilers. My control rods are the Sullivan carbon rods. The plane will spec-out routinely and is not bothered by moderate winds say less than 15mph.

[Creemy]

Thanks varoman. Servo city's Sanyo 1450mAh niMH square pack is almost an ounce heavier than a standard nicad pack. Might as well have the weight in battery capacity instead of lead.

[harlequin]

Creemy, I completed my Big Bird XL in June. Two HS-81s for rudder and elevator fit nicely side by side. I prepped the wings for spoilers for a possible future upgrade.

My battery is a 600 mah pack, and it's a tight fit into the front of the fuselage.

The plane is a great performer, but I have yet to spec it out like veroman1. More pilot skill needed. :D

Larry

[Creemy]

Thanks for the info on the pack and servos. I went ahead and ordered the 1450mAh NiMH pack which specs at the same width and height at a standard 600 square pack and only a hair longer so it should shoehorn in there. I also order 85MGs for the RE. The 81s are .47" wide and the 85s are .51". Should still fit side by side but no biggie if they won't. My building skills have probably atrophied along with my stick fingers the last few years so the plane probably won't be a featherweight. An extra bit of weight in the nose shouldn't hurt it. Also ordered an Optic 6 which sounds like a good match for this or any RES ship for that matter. I'll probably order a heftier trans battery as well. A 1450 rec. batt. will likely outlast a standard Hitec trans batt. by a bunch. Not that I'll be putting up long flights anytime soon but it'll be nice to fly all day if need be without needing a field charge.